1. Field of the Invention
The present invention relates generally to optical switching systems, and more specifically to an optical asynchronous transfer mode (ATM) switching system for broadband ISDN (Integrated Services Digital Network).
2. Description of the Related Art
A photonic packet switching system having input buffers is described in a paper "Photonic Packet Switch Based On VSTEP Two-Dimensional Array", S. Suzuki et al., Photonic Switching, 1991 Technical Digest Series Mach 6-8, 1991, Salt Lake City, Utah, Cosponsored by Optical Society of America, IEEE/Lasers and Electro-Optics Society. The input buffers are followed by an optical self-routing network for routing a packet, or ATM cell launched into the network from the buffers through an array of voltage-controlled optical gates to one of the outlets of the network depending on whether an electrical gating signal timely coincides with a header bit of the cell.
If an optical (N.times.N) self-routing network is implemented using the coincidental routing technique, N.sup.2 header bits would be required for routing ATM cells to any of the outlets of the network without collision with the other cells at the outlets due to the need to identify all positions of the outlets as well as the need to identify the inlets. This number would prohibitively increase as the number of inlets and outlets increases since the header bits degrade the throughput of the system. If priority control is implemented, an extra amount of timeslots would be required. Additionally, the known photonic switching system is not capable of meeting a desire that copies of a cell be routed simultaneously to several destinations.